Cracking catalyst improvement with gallium compounds

ABSTRACT

Gallium compounds are usefully employed to modify hydrocarbon cracking catalysts.

BACKGROUND OF THE INVENTION

The present invention relates to catalysts. In another aspect, thepresent invention relates to hydrocarbon cracking catalysts. In stillanother aspect, the invention relates to restoring the selectivity ofhydrocarbon cracking catalysts. in yet another aspect, the inventionrelates to cracking a hydrocarbon feedstock.

Contaminants, for example, nickel, vanadium, and iron are found insignificant concentrations in hydrocarbon feedstocks such as, forexample, heavy oil fractions and in lower quality crude oils. Thesecontaminants have a detrimental effect on the catalysts employed toconvert these oils into gasoline and other valuable petroleum products,making processing of these oils economically unattractive.Unfortunately, because of limited supplies of oils containing low levelsof contaminants, it is necessary to employ metals contaminated oils inhydrocarbon processes, such as catalytic cracking processes.

The contaminants found in feedstocks to cracking processes becomedeposited on the cracking catalyst. The deposition on the catalyst of,for example, nickel, vanadium and iron, causes a decrease in theactivity of the cracking catalyst to convert the hydrocarbon feedstockinto cracked products, including gasoline. The selectivity of thecracking catalyst for cracking the feedstock into gasoline as manifestedby the portion of cracked products comprising gasoline is alsodecreased. The production of undesirable products, for example, hydrogenand methane, which must be compressed, necessitating additionalequipment; and coke, which is deposited on the catalyst and must beburned off, requiring additional equipment and "off time", during whichthe catalyst is not employed for cracking, is significantly increased.

Because of these problems, the industry often replaces crackingcatalysts contaminated by more than about 3,000 parts per million (ppm)of vanadium equivalents and iron. As used herein, the term vanadiumequivalents is the measure of the combined parts by weight of vanadiumand four times the nickel per million parts by weight of crackingcatalyst including the weight of nickel, vanadium and iron on thecracking catalyst. There is thus a need for a cracking process suitablefor use with contaminated feedstocks and contaminated crackingcatalysts. There is also a need for a cracking catalyst which avoids atleast some of the detrimental effects caused by deposits thereon ofcontaminants selected from nickel, vanadium and iron. There is also aneed for a process of treating a contaminated cracking catalyst toincrease its selectivity for producing gasoline boiling range typeproducts.

OBJECTS OF THE INVENTION

It is thus an object of the present invention to provide a method forrestoring the selectivity of a contaminated cracking catalyst.

It is a further object of this invention to provide an improved crackingcatalyst wherein decreased catalyst selectivity caused by contaminantssuch as nickel, vanadium and iron on the cracking catalyst is mitigated.

It is another object of this invention to provide a process for crackinghydrocarbons wherein the deleterious effects caused by metals on thecracking catalyst are at least mitigated.

These and other objects of the present invention will be more fullyexplained in the following detailed disclosure of the invention and theappended claims.

SUMMARY OF THE INVENTION

In accordance with the present invention, a catalyst compositioncomprises a zeolite-modified cracking catalyst having deposited thereona treating agent selected from gallium and a compound of gallium.

Further, according to the invention, a contaminated cracking catalystpreviously employed for the catalytic cracking of hydrocarbons isimproved by contacting the cracking catalyst with gallium or a compoundthereof.

Still further in accordance with the invention, a hydrocarbon feedstockis catalytically cracked employing the above described catalystcomposition.

DETAILED DESCRIPTION OF THE INVENTION

It has been discovered that the adverse effects of nickel, vanadium andiron on a cracking catalyst can be mitigated by contacting the crackingcatalyst with a treating agent selected from gallium and galliumcompounds. The treating agent can be selected from most any source ofgallium such as elemental gallium, inorganic gallium compounds, andorganic gallium compounds. Suitable inorganic gallium compounds includesalts, for example, gallium nitrate, gallium sulfate, gallium oxide,gallium hydroxide, gallium phosphide, gallium nitride, gallium sulfide,gallium selenide, sodium gallate, calcium gallate, gallium antimonide,or gallium compounds that have the empirical formula GaM(SO₄)₂, where Mis NH₄ ⁺ or a member of Group IA of the periodic table, as found at page83 of the Handbook of Chemistry and Physics, 54th edition (1973-74),published by the Chemical Rubber Company Press, Cleveland Ohio. Lesspreferred, because of the corrosive effect of halogens on processequipment, are halogen-containing gallium salts, for example, GX₃ orGa(XO₃)₃, where X is selected from the group Cl, Br and I, Suitableorganic compounds can be represented generally by the formula GaR.sub. 3wherein R is an organic moiety. Included within this group are the saltsof carboxylic acids, (R'COO)₃ Ga wherein R' is hydrogen or a hydrocarbylradical having from 1 to about 20 carbon atoms. Examples of suitablecarboxyl compounds include gallium formate, gallium acetate, galliumpropionate, gallium butyrate, gallium decanoate, gallium stearate,gallium citrate, gallium lactate, gallium malate, gallium oxalate, andthe like. Polybasic carboxylates, such as gallium citrate, galliummalonate, and gallium oxalate can also be utilized. Other suitableorganic compounds are for example, gallium tris(hydrocarbyloxide)s--Ga(OR")₃ --wherein R' preferably contains one to about 20carbon atoms and can be an alkyl, alkenyl, cycloalkyl, or aryl radical,or a combination of radicals such as alkaryl, aralkyl, alkylcycloalkyl,and the like. Examples of suitable oxyhydrocarbyl compounds are galliummethoxide, gallium isopropoxide, gallium tert-butoxide, galliumphenoxide, gallium decyloxide, and the like. Other suitable organiccompounds are for example, gallium alkyls--GaR'"₃ --where R'" can be analkyl group containing 1-20 carbon atoms, preferably 1-5 carbon atoms.Examples of suitable hydrocarbyl compounds are triethylgallium,tributylgallium, diethylpentylgallium, and the like. It is recognizedthat these compounds are pyrophoric and must be treated accordingly, R',R", and R'" can be substituted with, for example, halogen, sulfur,phosphorus or nitrogen. For example, sulfur containing compounds such asgallium dialkyldithio-carbarnates and gallium xanthates are suitable.Also, gallium compounds containing both phosphorus and sulfur, forexample, gallium dihydrocarbyl dithiophosphates, such as thoserepresented by the formula Ga[S₂ P (OR'")₂ ]₃ wherein R'" is as definedbefore, are suitable. Of course, mixtures of any of the above compoundsmay be utilized. The gallium containing treating agent of this inventioncan also be utilized in combination with other passivating agents, forexample, passivating agents containing elements selected from GroupsIVA, VA and VIA of the Periodic Table, preferably antimony.

Generally, the amount of gallium containing treating agent contactedwith the cracking catalyst is a "passivating amount". By passivatingamount is meant an amount of treating agent which is sufficient tomitigate at least one of the deleterious effects caused by deposition onthe cracking catalyst of at least one contaminant selected from thegroup of nickel, vanadium and iron, such as, for example, decreasedcatalyst selectivity for gasoline production.

Although not intending to be bound to any particular theory ofoperation, it is believed that the decomposition products of the galliumcontaining treating agent react with the contaminants present on thecracking catalyst in such a way as to decrease the activity of thecontaminants for detrimentally affecting the cracking process. It istherefore believed that an effect of the contact between the crackingcatalyst and a passivating amount of gallium containing treating agentis an increase in the gallium concentration of the cracking catalyst.However, for many applications, the increased gallium concentration inthe cracking catalyst may be too small to measure.

Generally, a sufficient amount of the gallium-containing treating agentis contacted with the cracking catalyst to impart to the crackingcatalyst a concentration of added gallium of between about 1 and about100,000 parts per million (0.0001 to 10 weight percent) by weight ofcracking catalyst after treatment. Where a gallium-containing crackingcatalyst is treated, the added gallium will be manifested as anincreased gallium concentration in the cracking catalyst. It ispreferred to contact the cracking catalyst with a sufficient amount ofgallium-containing treating agent to impart to the cracking catalyst aconcentration of added gallium of between about 10 and about 10,000parts per million by weight (0.001 to 1 wt percent) of cracking catalystafter treatment, more preferably from about 100 to about 2,500 parts permillion (0.01 to 0.25 wt percent) because treated cracking catalystshave concentrations of added gallium within this range have been testedwith good results.

Generally, the amount of gallium added to the cracking catalyst shouldbe an amount sufficient to impart to the cracking catalyst a ratio ofweight of added gallium to vanadium equivalents on the crackingcatalysts of between about 1:1,000 to about 5,000:1,000. Morepreferably, the added gallium is in an amount sufficient to impart tothe cracking catalyst a ratio of weight of added gallium to vanadiumequivalents on the cracking catalyst of between 5:1,000 to 500:1,000.More preferably, the added gallium is in an amount sufficient to impartto the cracking catalyst a ratio of weight of added gallium to vanadiumequivalents of between about 20:1,000 to about 200:1,000, becausetreated cracking catalysts having weight added gallium:vanadiumequivalents ratios within this range have been tested with good results.

The present invention has particular utility for improving the crackingcharacteristics of cracking catalysts having deposited thereon 3,000 ppmand greater of vanadium equivalents. Untreated cracking catalysts haveusually developed undesirable cracking behavior at a contamination levelof 3,000 vanadium equivalents. Treatment of the cracking catalyst inaccordance with the present invention is effective to mitigate theundesirable behavior of cracking catalysts having deposited thereon3,000 ppm vanadium equivalents, 10,000 ppm vanadium equivalents and even20,000-50,000 vanadium equivalents and beyond of contaminants.

Any suitable method can be used to contact the treating agent with thecatalyst. It can be mixed with the catalyst as a finely divided solidand dispersed by rolling, shaking, stirring, etc. Or, it can bedissolved in a suitable solvent, aqueous or organic, and the resultingsolution used to impregnate the cracking catalyst--followed by drying toremove the solvent. Or, it can be sprayed on the catalyst, such as bybeing dissolved or suspended in the feedstock to a catalyst crackingunit.

The time required to effect a contact between the treating agent andcracking catalyst is not particularly important. Generally, for a batchtreatment outside of a catalytic cracker such time period can range from0 to 30 minutes. Likewise, the temperature at which the contact iseffected can be selected from a wide range of values, depending, forexample, on whether the treating agent is contacted with the crackingcatalyst as a vapor or as in solution with a relatively low boilingsolvent.

The cracking catalysts which can be advantageously treated in accordancewith the above-described process are generally any of those crackingcatalysts employed for the catalytic cracking of hydrocarbons boilingabove 400° F. (204° C.) in the absence of added hydrogen which havebecome partially deactivated by deposits of contaminating metalsthereon. Treatment of such contaminated cracking catalysts in theabove-described manner produces the modified cracking catalyst of thepresent invention. These cracking catalysts generally contain silica orsilica alumina and are frequently and preferably associated withzeolitic materials. Generally, from 1 to 40 percent, usually from about2 to about 10 percent by weight of the catalyst will comprisecrystalline zeolitic materials. The zeolitic materials can be naturallyoccurring or synthetic, and such materials can be produced by ionexchange methods and provided with metallic ions which improve theactivity of the catalyst. Zeolite-modified silica alumina catalysts areparticularly applicable to this invention because of their high activityand selectivity. Examples of metals contaminated cracking catalysts intoor onto which a source of gallium can be incorporated includehydrocarbon cracking catalysts obtained by admixing an inorganic oxidegel with an aluminosilicate, and aluminosilicate compositions which arestrongly acidic as the result of treatment with a fluid mediumcontaining at least one rare earth metal cation and a hydrogen ion, orion capable of conversion to a hydrogen ion.

It is inherent in this invention that the treated cracking catalyst willbe subjected to elevated temperatures. When utilized in a continuouscracking process, the treated cracking catalyst can be subjected totemperatures between 800° F. (427° C.) and 1200° F. (649° C.) in thecracking zone and temperatures between 1000° F. (538° C.) and 1500° F.(816° C.) in the regeneration zone. Generally free oxygen containing gasis present in the regeneration zone. The contacting of the treatingagent with the cracking catalyst can occur in the cracking zone, in theregeneration zone, or in the catalyst stream between the two zones.

A further embodiment of the present invention is directed to a catalyticcracking process wherein a hydrocarbon feedstock is contacted with theabove-described modified cracking catalyst under cracking conditions toproduce a cracked product. Such cracking operations are generallycarried out at temperatures between 800° F. (427° C.) and about 1200° F.(649° C.) at pressures within the range of subatmospheric to severalhundred atmospheres. A preferred example of this embodiment of theinvention utilizes a cyclic flow of catalyst between a fluidizedcracking zone and a regeneration zone in a cracking reactor. Generally,the cracking catalyst is in particulate form and has a size within therange of from about 10 to 100 microns, preferably about 60 microns,where fluidized bed cracking is utilized. Generally, a hydrocarbonfeedstock is introduced into a cracking zone under cracking conditionsincluding the absence of added hydrogen and contacted with the abovedescribed modified cracking catalyst to produce an effluent containingcracked product and cracking catalyst having coke deposits thereon. Thecracked products and unreacted feedstock are separated from the crackingcatalyst, and the cracking catalyst is regenerated by contact withoxygen-containing gas under regeneration conditions to remove at least aportion of the coke from the cracking catalyst by combustion usually ina regeneration zone apart from the cracking zone. The thus regeneratedcracking catalyst can then be recycled back to the cracking zone usuallywith supplementation by make-up catalyst for the cracking of additionalhydrocarbon feedstock. Such a system is well known to those skilled inthe art.

Specific conditions in the cracking zone and the regeneration zone of afluid catalytic cracker depend on the feedstock used, the condition ofthe catalyst, and the products sought. In general, conditions in thecracking zone include:

                  TABLE I                                                         ______________________________________                                        Temperature:                                                                           427-649° C. (800-1200° F.), preferably                          482-538° C.                                                   Contact time:                                                                          1-40 seconds, preferably 1-10 seconds                                Pressure:                                                                              10 kiloPascals to 21 megaPascals (0.1 to 205 atm.)                   Catalyst:oil ratio: 3/1 to 30/1, by weight                                    ______________________________________                                    

Conditions in the regeneration zone include:

                  TABLE II                                                        ______________________________________                                        Temperature:                                                                           538-816° C. (1000-1500°F.), preferably                          620-677° C.                                                   Contact time:                                                                          2-40 minutes                                                         Pressure:                                                                              10 kiloPascals to 21 megaPascals (0.1 to 205 atm.)                   Air rate (at 16° C., 100-250 ft.sup.3 /lb coke 1 atm.): (6.2-15.6      m.sup.3 /kg                                                                   coke)                                                                         ______________________________________                                    

The feedstocks introduced into the catalytic cracking unit are generallyoils having an initial boiling point of above 204° C., and an endboiling point which is frequently above 400° C. This includes gas oils,fuel oils, topped crude, shale oil and oils from coal and/or tar sands.

Such feedstocks can and usually do contain a significant concentrationof at least one metal selected from vanadium, iron and nickel. Becausethese metals tend to be concentrated in the least volatile hydrocarbonfractions suitable for use as feedstocks, a process for cracking theseheavy oil fractions is probably the most important embodiment of thisinvention. Currently, the industry obtains only economically marginalresults when cracking feedstocks containing from about 50 to about 100parts per million of total effective metals, where total effectivemetals is defined herein as the sum of the elemental weights of iron,vanadium and four times the weight of nickel in 1,000,000 parts byweight of feedstock, including the iron, vanadium and nickel containedtherein. In accordance with the present invention, feedstocks containing50-100 parts per million of total effective metals, and even thosecontaining 100-200 parts per million of total effective metals andbeyond can be economically cracked to produce gasoline and other lightdistillates. The quantity of added gallium required to passivatevanadium, iron and nickel is related directly to the concentration ofthese metals in the feedstock. In a preferred embodiment, the galliumcontaining treating agent is dissolved or suspended in a suitablesolvent and introduced into the catalytic cracking unit along with thehydrocarbon feedstock. Generally, a sufficient amount of thegallium-containing treating agent will be introduced into thehydrocarbon feedstock so as to impart to the feedstock a concentrationof gallium of between 1 and about 200 parts per million based on weightof feedstock entering the cracking zone. Usually, the concentration ofgallium in the feedstock will be between about 5 and 50 parts permillion by weight. It is advantageous to employ a concentration ofgallium on the cracking catalyst in relationship to the contaminatingmetals concentration in the feedstock as shown by the following table.

                  TABLE III                                                       ______________________________________                                        Total Effective Metals                                                                        Gallium Concentration                                         in Feedstock, ppm                                                                             on Catalyst, ppm                                              ______________________________________                                        ≦40-100   10-1,000                                                     100-200         25-2,500                                                      200-300         50-5,000                                                      300-800         100-10,000                                                    ______________________________________                                    

In another aspect of the present invention, it has been found that ametals-contaminated cracking catalyst which has been improved bytreatment with an antimony-containing treating agent is further improvedby treatment with a gallium-containing treating agent, particularly asregards gasoline yield when the cracking catalyst is employed in thecatalytic cracking of hydrocarbons. The benefit is observed even whenvery small amounts of gallium are used to promote the passivationeffects attributable to treatment with the antimony-containing treatingagent. Thus, the present invention includes within its scope crackingcatalyst compositions having deposited thereon both of anantimony-containing and a gallium-containing treating agent. Usually,the cracking catalyst will have an antimony concentration of betweenabout 0.01 to about 1 percent by weight, preferably from about 0.05 toabout 0.5 percent by weight. Usually, the cracking catalyst will have aconcentration of gallium of from about 0.001 to about 0.25 percent byweight. Usually, the gallium and antimony are employed on the catalystat elemental weight ratios of from about 1:1,000 to about 1000:1preferably at a weight ratio of from about 1:500 to about 5:1, and mostpreferably at a weight ratio of from about 1:100 to about 1:1, becausegood results have been obtained by treating the cracking catalyst witheach of a gallium-containing treating agent and an antimony-containingtreating agent to impart to the cracking catalyst weight (elemental)concentrations of gallium and antimony which fall within the mostpreferred ratio. Similarly, a cracking process in which anantimony-containing treating agent is introduced into the cracking zonetogether with the cracking catalyst, such as in admixture with thehydrocarbon feedstock, is improved by the introduction ofgallium-containing treating agent into the cracking zone.

The invention is illustrated by the following examples.

EXAMPLE I

Preparation of gallium diethyldithiocarbamate. This compound wasprepared by a double decomposition reaction between gallium chloride andpotassium diethyldithiocarbamate. The former was purchased from achemical supply house; the latter was synthesized as follows: to 43.0 g(0.769 moles) of potassium hydroxide and 56.3 g (0.769 moles) ofdiethylamine in a flask, 59.9 g (0.786 moles) of carbon disulfide wasdropped dropwise while the flask was cooled in ice water. A solidproduct was formed from the combination of these reactants. It wasdissolved in about 100 mL of tetrahydrofuran (THF), heated to theboiling point of THF, then cooled in ice water and solvent was removedby filtration. The nearly white crystalline product was washed withdiethyl ether. When dry the resulting potassium diethyldithiocarbamateweighed 137.4 g. A solution containing 25.1 g (0.134 moles) of it inabout 100 mL of THF was added to a cooled solution that contained 7.84 g(0.0445 moles) of gallium chloride in about 200 mL of THF. This mixturewas refluxed for five hours, cooled, filtered, and the solidrecrystallized from THF and n-hexane. Its composition, calculated as[(C₂ H₅)₂ NCS₂ ]₃ Ga, is 35.01 percent C, 5.89 percent H, 8.17 percentN, and 13.55 percent Ga; chemical analyses showed 35.79 percent C, 5.91percent H, 8.29 percent N, and 6.9 percent Ga. The reason for the lowconcentration of gallium is not known. However, the concentrationdetermined by the actual analysis provided the basis for calculating thequantity that was added to treat a cracking catalyst.

EXAMPLE II

Preparation of modified catalysts. Samples of a commercial crackingcatalyst (catalyst 0) that had been used in a commercial catalyticcracker until it had attained equilibrium composition with respect tometals accumulation (catalyst was being removed from the process systemat a constant rate) were modified by treatment with gallium. Thecatalyst, being a synthetic zeolite combined with amorphoussilica/alumina was predominantly silica and alumina. Concentrations ofother elements together with pertinent physical properties are shown inTable IV.

                  TABLE IV                                                        ______________________________________                                        Surface area       74.3 m.sup.2 /g                                            Pore volume        0.29 ml/g                                                  Composition                                                                   Nickel             0.38 weight percent                                        Vanadium           0.60                                                       Iron               0.90                                                       Cerium             0.40                                                       Sodium             0.39                                                       Carbon             0.06                                                       ______________________________________                                    

The catalyst contains 21,200 ppm vanadium equivalents of contaminants,i.e. combined parts by weight of vanadium and four times the nickel permillion parts by weight of cracking catalyst, including the weight ofnickel, vanadium and iron on the cracking catalyst.

Catalyst A was prepared by adding 0.108 g of powdered gallium oxide to80 g of equilibrium cracking catalyst and mixed by shaking in a jar for10 minutes. This catalyst contained 0.10 weight percent gallium.

Catalyst B was prepared by adding 0.040 g of antimony as antimonytris(O,O-di-n-propylphosphorodithioate) to 40 g of catalyst A. Fifty mLof dry cyclohexane was added to dissolve the antimony compound andfacilitate its distribution over the catalyst. After stirring themixture was heated until the solvent was evaporated. This catalystcontained 0.1 weight percent of gallium and 0.1 weight percent ofantimony.

Catalyst C was prepared by adding to 40 g of equilibrium crackingcatalyst 40 mL of toluene in which was dissolved 0.0295 g of the galliumcompound from example 1 and 0.040 g of antimony as antimonytris(O,O-di-n-propylphosphorodithioate). After thorough mixing solventwas removed by warming on a hot plate leaving a free flowing powder.This catalyst contained 0.005 weight percent gallium and 0.1 weightpercent antimony.

Catalyst D was prepared in the same way as Catalyst C but without anyadded gallium--it contained 0.1 weight percent antimony.

Before being used Catalysts A, B, C, and D were aged by subjecting themseparately to the following treatment. The catalyst, in a quartzreactor, was fluidized with nitrogen while being heated to 482° C., thenit was fluidized with hydrogen while the temperature was raised from482° to 649° C. Maintaining that temperature, fluidization continued for5 minutes with nitrogen, then for 15 minutes with air. The catalyst wascooled to about 482° C., still being fluidized with air. The catalystwas then aged through 10 cycles, each cycle being conducted in thefollowing manner. The catalyst at about 482° C. was fluidized withnitrogen for one minute, then heated to 510° C. during two minutes whilefluidized with hydrogen, then maintained at about 510° C. for one minutewhile fluidized with nitrogen, then heated to about 649° C. for 10 to 94minutes while fluidized with air, and then cooled to about 482° C.during 0.5 to 1 minute while fluidized with air. After 10 such cycles itwas cooled to ambient temperature while being fluidized with nitrogen,and was used in a run to crack gas oil.

EXAMPLE III

Catalysts A, B, C, and D were used in a fluidized bed reactor to crack agas oil. The cracking reaction was carried out at 510° C. andatmospheric pressure for 0.5 minute; regeneration was at about 649° C.,also at atmospheric pressure. The reactor was purged with nitrogenbefore and after each cracking step.

Properties of the gas oil used as feedstock for the cracking runs aresummarized in Table V.

                  TABLE V                                                         ______________________________________                                        API gravity at 15.6° C.                                                                      25.8°                                            BMCI                  41.1                                                    Carbon residue        0.87 weight percent                                     Sulfur                0.40 weight percent                                     Nitrogen              0.07 weight percent                                     Distillation (by ASTM D 1160-77)                                               2 percent            498° F.                                          10                    566                                                     20                    621                                                     30                    669                                                     50                    759                                                     70                    842                                                     90                    973                                                     95                    1047                                                    ______________________________________                                    

Results of the cracking runs are tabulated in Table VI.

                                      TABLE VI                                    __________________________________________________________________________                                                             Gasoline                                               Yields                 Selectively,                  Additive  Catalyst:Oil                                                                         Conversion,                                                                           Coke, Wt %                                                                            SCF H.sub.2 /bbl.                                                                    Gasoline,                                                                             Vol. % of            Run #                                                                             Catalyst                                                                           (Elemental Wt. %)                                                                       Weight Ratio                                                                         Vol. % of Feed                                                                        of Feed Feed Conv.                                                                           Vol. % of                                                                             Conversion           __________________________________________________________________________    1   O    None      7.7    64.5    8.7     635    51.7    80.2                 2   A    0.1 Ga.sup.1                                                                            7.67   61.8    9.1     660    55.4    89.6                 3   A    0.1 Ga.sup.1                                                                            7.7    60.3    8.1     690    53.8    89.2                 4   B    0.1 Ga.sup.1 + 0.1 Sb.sup.2                                                             7.7    64.0    7.8     521    58.5    91.4                 5   B    0.1 Ga.sup.1 + 0.1 Sb.sup.2                                                             7.67   66.8    8.0     452    58.6    87.7                 6   C    0.005 Ga.sup.3 + 0.1 Sb.sup.2                                                           7.55   62.8    7.4     387    58.6    93.3                 7   C    0.005 Ga.sup.3 + 0.1 Sb.sup.2                                                           7.56   63.9    6.6     355    58.8    92.0                 8   D    0.1 Sb.sup.2                                                                            7.7    64.5    6.0     410    54.8    85.0                 __________________________________________________________________________     .sup.1 via admixing with powdered gallium oxide                               .sup.2 via impregnation with antimony                                         tris(0,0di-n-propylphosphorodithioate)-                                       .sup.3 via impregnation with gallium diethyldithiocarbamate              

Comparison of the results from the average of two runs with Catalyst Awith those from untreated Catalyst 0show that at these conditionsCatalyst A produced a 5.6 percent higher yield of gasoline. Similarly,comparison of the results from the average of two runs with Catalyst Bwith those from Catalyst D show that the addition of 0.1 weight percentgallium to the catalyst that already bears 0.1 weight percent antimonyincreases the yield of gasoline by 6.7 percent. And comparison of theresults from the average of two runs with Catalyst C with those fromCatalyst D show that the addition of 0.005 weight percent gallium to thecatalyst that already bears 0.1 weight percent antimony increases theyield of gasoline by 7.1 percent.

The data from Table VI show certain unexpected results from treating thecatalyst with antimony and gallium combined. For example, the additionof 0.1 wt% Sb to a catalyst containing 0.1 wt% Ga caused, at about aconstant catalyst/oil ratio, an increase in conversion (activity) ofabout 3.6% (cf run 2 to run 4). Addition of 0.1 wt% of Sb to anequilibrium catalyst not containing Ga did not effect conversion to alarge extent (cf run 1 to run 8). The addition of 0.005 wt% Ga to anequilibrium catalyst containing 0.1 wt% Sb caused a reduction inhydrogen yield by about 5.6% (cf run 6 with run 8). The addition of 0.1wt% Ga to an equilibrium catalyst not containing Sb caused an increasein hydrogen yield of about 3.9% (cf run 2 with run 1).

What is claimed is:
 1. A composition comprising a zeolite modifiedhydrocarbon cracking catalyst containing from about 60 to about 99percent by weight of amorphous silica alumina matrix and from about 1 toabout 40 percent by weight of crystalline zeolitic material dispersedwithin the matrix and having deposited thereon a treating agent selectedfrom the group consisting of gallium and a compound of gallium in anamount sufficient enough to impart to the composition a concentration ofgallium of about 0.001 to about 1 percent by weight.
 2. A composition asin claim 1 which comprises from about 2 to about 10 percent by weight ofcrystalline zeolitic material.
 3. A composition as in claim 2 which hasa particle size within the range of from about 10 to about 100 microns.4. A composition as in claim 3 further comprising from about 3,000 toabout 50,000 parts per million by weight of vanadium equivalents ofnickel and vanadium deposited on the matrix and zeolitic material.
 5. Acomposition as in claim 4 further comprising from about 0.01 to about 1percent by weight of antimony expressed as the element deposited on thematrix and zeolitic material.
 6. A composition as in claim 5 comprisingfrom about 10,000 to about 50,000 parts per million by weight ofvanadium equivalents of nickel and vanadium deposited on the matrix andzeolitic material.
 7. A composition as in claim 6 comprising from about0.01 to about 0.25 weight percent of gallium deposited on the matrix andon zeolitic material.
 8. A composition as in claim 7 comprising fromabout 0.05 to about 0.5 percent by weight of antimony expressed as theelement deposited on the matrix and zeolitic material.
 9. A compositionas in claim 8 comprising from about 0.01 to about 0.1 percent by weightof gallium deposited on the matrix and on the zeolitic material.